The high-frequency signal injection method solves many of the problems of the permanent magnet motor without speed sensing control in zero- and low-speed operation, but its slow dynamic performance is also a major shortcoming. To address the dynamic response of high-frequency injection permanent magnet synchronous motor (PMSM) with speed sensorless control, an improved phase locked loop (PLL) structure based on variable structure sliding mode control is proposed. The structure is designed based on the traditional PLL, and the dynamic performance of the PLL is improved by performing the sliding mode control on the input signal of the PLL after the high-frequency signal is mediated. Compared with the traditional PLL structure, the method enhances the dynamic response of the system, and does not require motor parameters, and enhances the robustness of the system due to the introduction of the variable structure sliding mode function. Simulation and experimental results prove that the method shortens the motor dynamic response time and reduces the dynamic response overshoot, which proves the feasibility and effectiveness of the improved algorithm.